Chromosomal and plasmid-borne tigecycline resistance genes tet(X3) and tet(X4) in dairy cows in a Chinese farm.

We isolated 47 Acinetobacter spp. carrying tet(X3) and 4 ST767 E. coli strains carrying tet(X4) from 296 rectal swab samples from dairy cows in a Chinese farm. tet(X3) was located on chromosomes or diverse plasmids, and tet(X4) was located on IncFIBκ/FIA(HI1)/X1 non-transferable plasmid. Co-existence of tet(X3) and carbapenemase genes including blaOXA-58 and blaNDM-1 were detected in 9 Acinetobacter spp. These findings suggested the use of tetracycline and other antibiotics in food production warrants urgent attention.